Moisture And Mold On The Home Front
“Sensationalism and bias dominate mold discussions,” said Charles Culp, Ph.D., P.E., Texas A&M University, College Station, Texas, chair of the public session. The reason for the session, he said, was to offer facts that can help keep the media hype in perspective.
It takes exposure to a lot of mold for a person to develop an allergic response, according to Joseph Jarvis, M.D., University of Nevada, Reno. Jarvis talked about “The Health Effects of Indoor Mold Exposure.”
“All mold may be potential allergens,” said Jarvis. It takes a lot of mold exposure before a person becomes truly allergic, he said; then it takes a small dose to bring about an allergic response, such as allergic rhinitis, asthma, and hypersensitivity pneumonitis.
It may be inferred that if HVAC contractors and technicians are repeatedly exposed to high levels of mold during their work, they could develop a mold allergy. “The prognosis depends upon the length of time in exposure after symptoms begin,” Jarvis commented.
Homeowners have panicked about even small, relatively harmless amounts of mold because of consumer media hype, he said. “Nobody reports about mold. They report about toxic mold.” Relatively healthy people are “highly resistant to mold infection.
“The dose [of mycotoxin] makes the poison,” Jarvis said. “The route of exposure also makes the poison.” For example, it would require four months of daily exposure to 1,000 spores per cubic meter to accumulate a toxic dose, he said. People whose immune systems are weakened by age and/or disease are more vulnerable to mold infection.
Legal IssuesWhen it comes to protecting your company, who better to ask than a lawyer? Attorney Maralynne Flehner, King of Prussia, Pa., gave a fast-paced talk on “Mold Claims: The Liability of HVAC Industry Members and Building Owners Under the Law.”
“Oh no, the lawyers are here,” she joked, adding that mold claims are up 300 percent since 1999. She also stated that the best protection comes from your own attorney, and that her portion of the session was not meant to take the place of personal legal advice.
Mold case defendants have included contractors, designers, consultants, architects, school boards — “anyone who has anything to do with buildings.” Among the reasons they are being cited are negligence, warranties (breach of, implied, and explicit), strict liability, and fraud.
Damages being claimed include personal injury for asthma and upper respiratory tract infection; neurological damage and loss of consortium; property damage; punitive damages; and attorneys’ fees. Judgments thus far have ranged “from hundreds of thousands of dollars into the millions,” Flehner said.
The good news, she continued, is, “There’s a lot you can do to protect yourself.” For example:
“Most of all, get a good lawyer!”
System SavvyRay Patenaude, P.E., is with The Holmes Agency Inc. in St. Petersburg, Fla. He spoke about “Residential and Small Building Humidity and Mold Control.”
Certain conditions need to exist in order for mold to bloom and grow. “You’ve got to have moisture, you’ve got to have food, and you may have visitors in the room,” Patenaude said.
When Willis Carrier first designed air conditioning, his first priority was controlling humidity; air temperature was a secondary consideration, said Patenaude. “I put it to you that we have been controlling temperature, and therein lies the problem.”
Then the industry tried to solve IAQ problems with dilution. If that means the systems are drawing in moist air, that outside air requires more dehumidification, he pointed out. “The cooling coils will have to remove more moisture.”
Current load calculations provide better data for the removal of moisture part-load conditions, he said. This takes into account that the house itself is part of the HVAC system. “It’s not just a unit. The habitable space is a plenum. We need to understand uncontrolled airflow. The air conditioning doesn’t operate in a vacuum.”
In short, Patenaude said design and installation contractors need to understand:
In air conditioning systems, “Bigger is not better,” Patenaude said. Oversized systems re-evaporate moisture back into the living space.
Correct installation of refrigerant lines and ductwork “is extremely important,” he said. And above all, cooling systems require “maintenance, maintenance, maintenance,” to continue to operate as designed.
Joseph Lstiburek, Ph.D., P.Eng. with Building Science Corp., Westford, Mass., asked, “What Happened? Why Mold and Why Now?”
“The reason we have more mold problems is because we have more mold,” he stated.
“Mold has been around a long time,” he pointed out. “We’ve always had roof leaks, plumbing leaks, window leaks, and rain during construction.”
The difference now, he said, is that “Buildings don’t dry as quickly as they used to. The materials we build out of are much more moisture sensitive — they can’t take the moisture ‘events’ the way the old materials did.”
Mold is also a water problem, Lstiburek reiterated: “No water, no mold.
“Moisture moves from warm to cold,” he explained. The standardization of building codes essentially “gives this law of nature the finger,” Lstiburek said. “Buildings should be suited to their environment. This whole concept of standardization is hurting us.”
He assessed current building materials: “We need to build with trees. It’s tough for mold to attack.” Plywood, he said, is peeled off wood, baked, caramelized: “mold candy.” Flake board, cardboard, and fiberboard all become progressively easier for mold to eat. When you get to paper-faced gypsum, “Even old mold with no teeth can eat paper,” Lstiburek said. “Even the dumbest of the three little pigs didn’t build his house out of this.”
Finally, combining vinyl wallpaper and air conditioning “is madness” in some climates, he said.
“Our focus has been on the prevention of getting wet. We need to focus on drying the inevitable wetness.”
Glenn Hourahan, P.E., vice president of Research and Technology for the Air Conditioning Contractors of America (ACCA) in Arlington, Va., covered a topic that should be near and dear to contractors’ hearts: “Moisture Control — Achievable Through Accurate Load Determination and Proper Equipment Selection.”
Comfort, equipment, economics, and health are all related aspects of oversizing, he said.
“Why mold, why now? Because the load was guessed at. An ‘on-hand’ unit was installed. The contractor assumed that the existing size was OK,” said Hourahan.
Even when contractors run load calculations, many still add to the chosen unit’s capacity “to be on the safe side.” Not only is this not safe, said Hourahan, it is inappropriate. If a contractor is going to take the time to do a proper load calculation, he or she should install equipment according to its results.
Hourahan outlined some basic steps contractors should take when new air conditioning equipment will be installed:
1. Look at the building. What are the ventilation, occupant, and/or zoning needs? Appearance issues, fuel type, and overall budget need to be taken into consideration.
2. Perform a load calculation (Manual J, Version 8). This includes building parameters such as solar orientation, insulation, and envelope tightness.
3. Determine design conditions.
4. Ascertain sensible and latent loads, at full-load (sunny, hot day) and part-load (rainy, cool night) conditions.
5. “Avoid overly conservative safety factors,” he said. Do include diversity factors.
6. Select equipment using the manufacturer’s application data.
If standard equipment can’t satisfy full- or part-load conditions, consider controls, dual- and variable-speed equipment, wrap-around heat pipes, and optional evaporative coils. “It probably costs more, but tell the customer so you can charge appropriately,” said Hourahan.
Other humidity-control strategies to consider include reducing the evaporator operating temperature and overcooling with reheat, which requires independent control of temperature and RH. These options need to be considered on a case-by-case basis, he said.
Builders And InsurersThe perspectives of the home building and insurance communities rounded out the program.
Thomas Kenney, P.E., of the National Association of Home Builders (NAHB) Research Center, Upper Marlboro, Md., offered the “Homebuilders’ Perspective on Mold in Residential Buildings.” (“My comments aren’t the policy of NAHB,” he pointed out.)
“We’ve been working on this issue [mold] several years now,” he said. He pointed out what he considers to be mold myths vs. facts. For example:
Myth: Building materials have contributed to the mold increase.
Fact: “There is no proof of this. Homes are tighter now.”
Not every mold case is cause for alarm, he said. However, mold tends to gets worse when left untreated.
Incorporating many of the proposed changes to new homes “could affect low-income and entry-level home buyers,” he said, raising the cost of the homes beyond their means. It might be better to work with trade contractors for appropriate products.
David Golden, of the National Association of Independent Insurers in Des Plaines, Ill., gave the “Insurer’s Perspective on Mold in Residential Buildings.” He called the current state of mold, media, and misrepresentation “a three-ring circus. It’s just mold,” he added.
Why now? Like Lstiburek, he pointed out that “Mold loves to munch modern materials.”
All lines of modern insurance are involved in mold coverage, he said. Still, in most if not all homeowner policies, “The mere existence of mold was never covered.”
Although there is less media hype than there was about a year ago, mold is still commonly referred to as being “toxic.” Extreme cases are still being reported.
He said the media hype reminded him of a quote from Winston Churchill: “A lie gets halfway around the world before the truth has a chance to get its pants on.”
Building professionals need to clarify their insurance coverage, changes, and options, he advised. Provide information to help reduce customer anxiety. Recognize how expensive mold problems can be.
Still, “This is mold, not asbestos,” he said. The building community needs to do its part to “debunk bad information.”
Sidebar: Mold Under The Microscope“I spend most of my time inspecting moldy buildings,” said Philip Morey, Ph.D., to the appreciative audience at the ASHRAE public session on “Residential and Small Building Humidity and Mold Control.”
Morey, who is with Air Quality Sciences Inc. in Gettysburg, Pa., spoke about “Microbial Investigation Strategy and Interpretation.” He provided some of the most basic information about mold and how it grows.
Molds, he said, include fungi such as yeast and mushrooms. It lives in soil, and its growth is encouraged by moist, warm environments.
Spores are “born to fly,” Morey said. Spores are sent forth from existing mold to germinate new growth.
Why all the concern about mold now?
“We use a lot of construction materials that rot,” he said, such as amorphous cellulose. Older homes used hardwoods, terra cotta, etc., he pointed out. When homes leak, “Moisture is trapped in building walls,” he said.
Mold health risks are proportional to the amount of square feet the visible mold covers, Morey explained. Mold grows very quickly (24 to 48 hours for “baby” mold, seven days for viable mold).
Any cleanup must be done safely, and it must remove the underlying problem (moisture and dust), he pointed out.
“Inspect buildings for visible mold growth and water damage,” he said. Keep in mind that the humidity of surfaces is more important than the RH of the air.
— B. Checket-Hanks
Publication date: 03/17/2003